Methods and materials for transferring heat across the interface between a heat-dissipating component, which typically includes various electronic components in semi-conductor devices, to an external heat dissipater or heat sink are well-known in the art. In this regard, the electronic component generates substantial heat which can cause the component to fail catastrophically. Even to the extent the component does not fail, such elevated temperatures can and frequently do affect the component's electrical characteristics and can cause intermittent or permanent changes. Indeed, the life of an electronic component is directly related to its operating temperature, and a temperature rise of so much as 10° C. can reduce the component's life by 50%. On the other hand, a corresponding decrease in 10° C. can increase a component's life by 100%.
According to contemporary methodology, the typical solution to such heat dissipation problems is to provide an external heat dissipater or heat sink coupled to the electronic device. Such heat sink ideally provides a heat-conductive pathway from the heat dissipating component to outwardly extending structures such as fins or other protuberances having sufficient surface area to dissipate the heat into the surrounding air. To facilitate such heat dissipation, a fan is frequently utilized to provide adequate air circulation over the fins or protuberances.
However, essential to any effective system for removing heat from an electronic component to a heat sink requires efficient and uniform heat transfer at the interface between the component and the heat sink. Among the more efficient means by which heat is transferred across the interface between the component and the heat sink has been the use of heat conductive pads. Such heat conductive pads are typically pre-formed to have a shape or footprint compatible with a particular electronic component and/or heat sink, such that a given pad may be easily applied thereto prior to coupling the heat sink to the electronic component.
Exemplary of such contemporary phase change pad-type thermal interface products are THERMSTRATE; ISOSTRATE and POWERSTATE (each registered trademarks of Power Devices, Inc. of Laguna Hills, Calif.). The THERMSTRATE interface comprises thermally conductive, die-cut pads which are placed intermediate the electronic component and the heat sink so as to enhance heat conduction there between. The THERMSTRATE heat pads comprise a durable-type 1100 or 1145 aluminum alloy substrate having a thickness of approximately 0.002 inch (although other aluminum and/or copper foil thickness may be utilized) that is coated on both sides thereof with a proprietary thermal compound, the latter comprising a paraffin base containing additives which enhance thermal conductivity, as well as control its responsiveness to heat and pressure. Such compound advantageously undergoes a selective phase change insofar as the compound is dry at room temperature, yet liquefies just below the operating temperature of the great majority of electronic components, which is typically around 50° C. or higher, so as to assure desired heat conduction. When the electronic component is no longer in use (i.e., is no longer dissipating heat), such thermally conductive compound resolidifies once the same cools to room temperature.
The ISOSTRATE thermal interface is likewise a die-cut mounting pad and utilizes a heat conducting polyamide substrate, namely, KAPTON (a registered trademark of DuPont) type MT. The ISOSTRATE thermal interface likewise is a proprietary paraffin-based thermal compound utilizing additives to enhance thermal conductivity and to control its response to heat and pressure.
Additionally exemplary of prior-art thermal interfaces include those disclosed in U.S. Pat. No. 5,912,805, issued on Jun. 15, 1999 to Freuler et al. and entitled THERMAL INTERFACE WITH ADHESIVE. Such patent discloses a thermal interface positionable between an electronic component and heat sink comprised of first and second generally planar substrates that are compressively bonded to one another and have a thermally-conductive material formed on the outwardly-facing opposed sides thereof. Such interface has the advantage of being adhesively bonded into position between an electronic component and heat sink such that the adhesive formed upon the thermal interface extends beyond the juncture where the interfaces interpose between the heat sink and the electronic component.
Exemplary of the processes for forming thermal interfaces according to contemporary methodology include the teachings set forth in U.S. Pat. No. 4,299,715, issued on Nov. 10, 1981 to Whitfield et al. and entitled a METHODS AND MATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE; U.S. Pat. No. 4,466,483, issued on Aug. 21, 1984 to Whitfield et al. and entitled METHODS AND MEANS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE; and U.S. Pat. No. 4,473,113, issued on Sep. 25, 1984 to Whitfield et al., and entitled METHODS AND MATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE, the contents of all three of which are expressly incorporated herein by reference.
In addition to the construction of thermal interfaces, there have further been advancements in the art with respect to the thermal compositions utilized for facilitating the transfer of heat across an interface. Exemplary of such compounds include those disclosed in U.S. Pat. No. 6,054,198, issued on Apr. 25, 2000 to Bunyan et al. and entitled CONFORMAL THERMAL INTERFACE MATERIAL FOR ELECTRONIC COMPONENTS, and U.S. Pat. No. 5,930,893, issued on Aug. 3, 1999 to Eaton and entitled THERMALLY CONDUCTIVE MATERIAL AND METHOD OF USING THE SAME, the teachings of which are expressly incorporated by reference.
Such compositions, along with the aforementioned pad-type thermal interfaces, however, are each intended to be applied or positioned in a flat, horizontal plane (i.e., an X/Y axis) that runs parallel between the electronic component and heat sink. As a consequence, heat must pass through such materials via a parallel horizontal plane. As is well-known, however, the ability of a material to conduct heat is typically lower across a generally parallel or horizontal cross-section of material than could be attained through the same material maintained in a generally perpendicular or vertical orientation (i.e., a Z axis).
Notwithstanding the increased thermal conductivity along the vertical axis, contemporary methodology predominately emphasizes a thermal interface construction that is as thin as possible and/or utilizes a minimal amount of layers that are present between the heat sink and electronic component. Accordingly, there has not yet been available any type of thermal interface which concomitantly possesses a thermally-conductive material or substrate disposed in a vertical orientation (i.e., perpendicular relative the electronic component and heat sink) that additionally is thin enough to optimally facilitate the transfer of heat from the electronic component to a heat sink. There is also lacking any such type of thermal interface that can be readily fabricated from well-known, thermally-conductive materials that can be readily deployed in virtually all types of heat transfer applications requiring the dissipation of heat from an electronic component to a heat sink. Still further, there is lacking any type of thermal interface of the aforementioned variety that is easy to handle and utilize, effective in filling voids between and transferring heat away from a given heat-dissipating component to a heat sink, is easy and relatively inexpensive to produce, and does not require special handling.